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consisting of a retort (23 X 14-5 X 12 cm.) in which 15 c.c. of the oil are
gasified. The temperature of gasification is measured with a pyrometer
and the volume of gas produced and the components absorbable by fuming
sulphuric acid determined.

Another apparatus for this purpose has been proposed by Wernecke
and modified by Hempel.1 The results obtained on the laboratory scale
are, however, not accurate, the best method being the works test.

The following determinations may also be required : Specific gravity,
behaviour on distillation, flash point, viscosity, calorific power and sulphur,
these being carried out as indicated in the articles dealing with crude petroleum
and heavy oils.

Middle or gas oils are used for making illuminating gas, for carburetting
water gas, as a motive force, as a cleaning oil, and also as solvent.2

The yields from i kilo of oil vary between the following limits : gas, 500-600
litres ; tar, 300-400 grams ; coke, 40-60 grams.

(Lubricating Oils)

These oils vary somewhat in colour, appearance and consistency. The
colour is usually reddish, brown or blackish, and marked fluorescence is
also observed; some such oils are, however, colourless or yellowish and
not at all or but slightly fluorescent (vaseline oil). The smell is similar
to that of lamp oil if more volatile oils are present, but very heavy oils are
odourless. A bituminous smell indicates faulty refining and a tarry or
resinous odour the presence of extraneous matter. As a rule, these oils
are liquid and more or less viscous, but some are highly mobile and others
have almost the consistency of fats.

Analysis of lubricating oils aims at ascertaining if their characters are
in correspondence with the uses for which they are designed or with the
conditions fixed in the purchase contract.

Both physical and chemical tests are made.

1. Physical Tests

1. Colour.'This is usually compared with that of a selected oil by
means of the colorimeter (see Lighting Oil) or more simply by observing
equally thick layers of the two oils in similar rectangular bottles.

It should be borne in mind that heavy oils may be coloured artificially.
Aniline dyes are usually employed for this purpose and may be extracted
from the oil by water or dilute alcohol in presence of acid or alkali and
characterised by the tests to be given under the heading, Colouring Matters.

The standard colour for the fiscal classification of heavy mineral oils is that
of a 0-75% solution of pure, crystallised potassium chromate, this being com-
pared by transmitted light with the oil in question in an equally thick layer.

1  Journal fur Gasbekucbtung, 1910, p, 78.

2  For this purpose oils of lower density and solar oils from the distillation of shales
are also used.of the latter. The amount of gas given is determined